Corrosion inhibitors for refining &amp; petrochemical processing equipment

ABSTRACT

A process for the prevention of corrosion in refinery systems by the injection of an imidazoline compound into the overhead vapor line. The imidazoline compound is formed from the reaction of a naphthenic acid and dipropylene triamine.

iie tates fieiiens E aient 1 [451 on, M, 11073 QURROSKON INHIBHTURS FORREFINING & PETROCHEMICML PROCESSING EQUIPMENT [75] Inventor: Wililiam E.Seffens, Houston, Tex. [73] Assignee: Naico Chemise] Company, Chicago,

Ill.

[22] Filed: June 29, 11972 [21] Appl. No.: 267,333

[52] ILS. C11 208/47, 21/27, 208/187, 208/350, 203/7 [51] lint. C11...C23i 111/10, C07d 49/34, ClOg 9/16 [58] Field of! Search 208/47, 350;21/27; 203/7 [56] References Cited UNITED STATES PATENTS 2,466,5174/1949 Blair et al. 252/855 2,908,640 10/1959 Daugherty 208/3512,938,851 5/1960 Stedman et a1. 3,510,282 5/1970 Seffens 44/63 PrimaryExaminer-Delbert E. Gantz Assistant ExaminerG. E. SchmitkonsAttorney-John G. Premo et al.

[5 7] ABSTRACT 4 Claims, No Drawings CORROSION INHIBITORS EOE REEINTNG &EETEOCI'IEWIICAL PROCESSING EQUIPMENT INTRODUCTION This inventionrelates to a process for the prevention of corrosion in refinery systemsby injecting an imidazoline compound into the overhead vapor line. Morespecifically, this invention relates to the addition of an imidazolinecompound having corrosion inhibition properties to the refinery system,the imidazoline being capable of preventing corrosion inside therefinery system. The preferred imidazolines are formed by the reactionof dipropylene triamine and naphthenic acid.

The imidazoline surfactant is known to the art as a corrosion inhibitor.The composition and its use as a corrosion inhibitor in motor fuel andon metal surfaces is disclosed in U. S. Pat. No. 2,466,517 and U. S.Pat. No. 3,510,282, the specifications of which are to be incorporatedby reference in its entirety. In particular, the imidazoline surfactantformed by the reaction of dipropylene triamine and a naphthenic acid isdisclosed as a corrosion inhibitor.

In refinery processing there is usually a significant amount of waterpresent with the crude petroleum. Water is present with the crudepetroleum when it is extracted from the ground. In addition, substantialamounts of water are present from condensation resulting from the use ofsteam in the distilling stage. In refinery processing due to thepresence of both water and crude petroleum, it has been found that thewater and crude petroleum easily mix, the result being the formation ofan emulsion. When such an emulsion is formed it is often quite timeconsuming and expensive to break the emulsion to rid the system of thewater. It, therefore, would be desirable to inject into the system achemical which would prevent or reduce this emulsion formation.

It has been found that when the imidazoline compound is injected into arefinery system, in addition to its corrosion inhibition properties, italso exhibits the ability to reduce formation of an emulsion of waterand crude petroleum.

OBJECTS lt is an object of this invention to provide a process for theprevention of corrosion in refinery systems by injecting into theoverhead vapor line an imidazoline compound.

It is an object of this invention to provide an imidazoline compound toprevent emulsion formation between water and the crude petroleum inrefinery processing.

it is also an object of this invention to provide an imidazolinecompound useful in preventing emulsion formation between water and crudepetroleum in refinery processing, said surfactant having corrosioninhibition properties.

It is a further object of this invention to provide an imidazolinecompound formed by the reaction of dipropylene triamine and naphthenicacid, said compound preventing emulsion formation of water and crudepetroleum in refinery processing.

Further objects will appear hereinafter.

THE INVENTION This invention relates to a process for the prevention ofcorrosion in refinery systems comprising the step of injecting into therefinery system a composition consisting of:

A. from 1040 percent by weight of an organic sol vent; and

B. from 60-90 percent by weight of an imidazoline compound havingcorrosion inhibition properties, said compound formed by the reaction ofdipropylene triamine and a naphthenic acid in the ratios of 1:2 to 2:1.

The preferred composition consists of:

A. 20 percent by weight of an organic solvent; and

B. percent by weight of an imidazoline surfactant having corrosioninhibition properties, said surfactant formed by the reaction ofdipropylene triamine and a naphthenic acid in the ratio of 1:2.

ORGANIC SOLVENT The organic solvent of the composition acts merely as asolvent or carrier for the imidazoline surfactant. The organic solventmay be aliphatic or non-aliphatic liquid. Generally, the organic solventis a hydrocarbon liquid having from 3 to 22 carbon atoms. Typically,high boiling aromatic organics are used in the practice of thisinvention. For example, kerosene is a preferred organic solvent. Othersolvents which may be used are propane, butane, and heptane. The organicsolvents used in this invention are not limited to those mentioned abovebut include a large type and variety of organic solvents in which theimidazoline surfactant is soluble.

IMIDAZOLINE SURFACTANT The imidazoline surfactant of this invention isformed by the reaction of dipropylene triamine and a naphthenic acid ina ratio of 1:2 to 2:1. The preferred ratio of dipropylene triamine tonaphthenic acid is 1:2. It has been found that when ratios of thedipropylene triamine to naphthenic acid outside the above mentionedrange are used, an inferior imidazoline surfactant is obtained which isnot as efficient in preventing the formation of an emulsion betweenwater and the fuel.

The naphthenic acid used in this invention is defined in US. Pat. No.3,510,282 as being a petroleum refining by-product obtained when thealkali liquor from the caustic treatment of gas oil is acidified withsulfuric acid. This treatment produces a dark brown about 12 on theGardner color scale (when out 1 to 9 with mineral spirits) oily liquidwhich separates to the top of the aqueous liquor. The mixed acids can bedivided roughly into three groups having the general formulas: C,,H ,,OC H O and C l-I ,O The first group occurs largely in the lower boilingfraction of the mixture. They usually contain 6 or 7 carbon atoms andare colorless.

The second group, usually the largest, contains acids of 8 to 12 carbonatoms having the structure:

Ha 0 CH3 The third group contains the heaviest molecules which arepolycyclic and have from 12 to 23 carbon atoms.

All fractions from a carefully distilled naphthenic acid (24) containsome color which, so far, has proved impossible to remove. Tarryresidues account for the dark color of the crude, but these are largelyremoved by distillation. Since naphthenic acids are saturated andprimarily cyclic, their soaps have much greater stability than those ofother common liquid acids. The crude acid as delivered has a density of8.04 to 8.44 pounds per gallon and a viscosity of 1.25 poises at 77 F.The acid values range from 160 to 270, but naphthenic acid used for soapmanufacture usually has an acid value between 220 and 230. pH of thewater extract is about 5.5 and the iodine value between 8 and l 1.Unsaponoifiables are held below 12 percent. The initial boiling pointsvary widely from shipment to shipment. Individual batches have boiledbelow 200 F. and up to almost 400 F. at 3.5 inches of mercury.

A typical formula in connection with some of the commercially availablenaphthenic acids is the followmg:

CH: CH: H

These particular acids are available in at least three different grades;Grade 1 having an average molecular weight of 290-300. Generallyspeaking, there is present about 6 percent of non-saponifiables and thistype is perhaps characteristic of the most common commercially availablenaphthenic acid.

Grade 2 has a somewhat higher molecular weight, for instance 320-330 andcontains about 8 percent of nonsaponifiable matter. Grade 3, which findsconsiderable utility, has a molecular weight range of 410-420 andcontains about l0 percent nonsaponifiable matter.

Any naphthenic acid may be used but preference is to use the commercialgrades above described, or in some instances, mixtures of two differentgrades so as to give, for example, an average molecular weight of 360 to370 in some instance, and in others, a molecular weight of about 3 l0,or thereabouts.

in examining the formula immediately preceding, with the formulapreceding the above formula, and ignoring difference in the cyclicstructure of the naphthenic acids, it is apparent that in at least somenaphthenic acids which are available commercially the cyclic structureis part of the beta carbon atom. On the other hand, as far as is known,and referring to the for-- mule.

- Hi H:

HI L

there are available nEEhYiTeEE acids in which appar-. ently x in theformula represents a small whole number,

for instance, 3 or 4 or the like.

In practicing the present invention preference given to the highermolecular weight naphthenic acids, for example those having an averagemolecular weight of at least about 2,000 such as about 250 to 500, or

greater, for example from about 290 to 420 but preferably from about325-375.

Since commercial grades of naphthenic acids are employed, these containmany individual species over a molecular weight range. p

The most preferred naphthenic acid those known as Sunaptic acids whichare high-molecular-weight naphthenic acids prepared by the causticextraction of selected base stocks. They range in acid number from TABLEI.SPECIFICATIONB Sunaptic Acids A Sunaptic Acids B Sunaptic Acids CSpeclfi- Typical Specifi- Typical Specifi- Typical cation analysiscation analysis cation analysis Acid number, mg. KOH/g 170-180 172150-160 157 120-130 12 Unsaponiflables, percent by wt. 4 7 6. 3 4 7 5.04 11 Density, 20/4 Specific gravity at F. API gravity at 60 F..Viscosity, SUS at 210 Bromine number Refractive index, nD Pour point,deg. F Flash point, deg. F Sulfur content, percent by weight Averagemolecular weight 3 Distillat on range, deg. F. at 2 mm. Hg:

Initial Percent recovery AOCS CAL-40. 2 ASTM D-1158-52I.

3 Calculated from acid number and percent unsaponifiable.

l Maximum. Minimum.

THE DIPROPYLENE TRlAMlNE The amine that reacts with the naphthenic acidto form the imidazoline surfactant of this invention is dipropylenetriamine. Qne molecule of dipropylene triamine reacts with two moleculesof naphthenic acid to form two isomers:

One molecule of dipropylene triamine reacts with one molecule ofnaphthenic acid to form two isomers:

Thus, there are four possible imidazoline surfactant isomers which maybe formed from the reaction of dipropylene triamine and naphthenic acid.

APPLICATION As mentioned above, water is usually present in the refinerysystem. Water is present with the crude petroleum when extracted fromthe ground and, in addition,

3 substantial amounts of water are present from condensation resultingfrom the use of steam in the distilling stage. In order to prevent theformation of an emulsion between the water and the crude petroleum, theimidazoline surfactant is injected into the refinery system.

The imidazoline surfactant is generally diluted by an organic solvent.The preferred concentration of the imidazoline surfactant is percent byweight.

The diluted imidazoline surfactant can be injected at numerous stages ofthe refinery system. The preferred points of injection are at theoverhead vapor line and at the reflux line. Generally, the compositionis injected as a spray. The imidazoline surfactant will distributethroughout the system preventing formation of an emulsion as well aspreventing corrosion on the metal surfaces inside the refinery unit.Generally from 2-5ppm of the composition is injected.

To further illustrate the invention, the following examples arepresented:

EXAMPLE 1 At a petroleum refinery in Southern California, an imidazolinesurfactant dissolved in kerosene was injected into the overhead vaporline as a fine spray. The

The imidazoline surfactant was prepared by the reaction of dipropylenetriamine and a commerical naphthenic acid in a molar ratio of 1:2. Thenaphthenic acid used in the Examples is derived from petroleum and is anorganic acid containing a substituted naphthenic ring structure. Thenaphthenic acid has the following properties:

The reactants were charged to reactor and heated to 170C. for 30 minutesat which time a vacuum of about 28 inches was applied for an additional4 hours. The product was cooled and dissolved in the heptane.

The composition was injected in a concentration of l2ppm. Samples of thefuel were removed from the refinery system and the amount of wateremulsified was measured by using the test procedure ASTM D 2550. This isa measure of transmittance with the WlSM values ranging from 0-100 withthe higher WlSM value indicating lower amounts of water present. TheWlSM value obtained was 97.

Typical WlSM values obtained using other surfactants are listed in TableIII.

TABLE Ill SURFACTANT PPM WlSM Value Diethylene triamine Naphthenic Acid20 Diethylene triamine Oleic Acid 20 Dipropylene triamine NaphthenicAcid 20 93 Dipropylene triamine Linoleic Acid 20 67 It is observed fromthe data presented above that the imidazoline surfactant of thisinvention results in substantial reduction in the amount of water heldin emulsion with the crude petroleum.

EXAMPLE Ill The corrosion rate of the imidazoline surfactant as preparedin Example I was measured as compared to the corrosion rates of thesurfactants listed in Table lll. The resulting corrosion rates aretabulated in Table IV.

The corrosion rates were determined by use of the following procedure:

Through the scale neck of a 1000 ml round bottom, three-neck Pyrex flaskhaving a gas dispersion tube inserted through a cork stopper and acoupon holder is inserted 425 cc of depolarized naphtha and 225 cc ofrefinery stream water.

The refinery stream water is deionized water containing 1000 ppmhydrochloric acid and 500 ppm acetic acid. The pH of the water isadjusted to 7.5 with ammonium hydroxide. The surfactant is also added atthis point. The gas tube holder is inserted into the flask neck and theflow of gas started. The gas consists of 93 percent prepurifiednitrogen, 5 percent air and 3 percent hydrogen sulfide and is fed at arate of 40 cc/min./test through calibrated capillary tubings. The conedrive motor is turned on as is the heating mantle. The test is allowedto run for an hour before the coupon is inserted to attain equilibrium.The coupon is positioned such that the gas dispersion tube is on thedownstream side of the coupon, the gas makes a complete circuit of theflask before it hits the coupon.

The corrosion coupon is a 0.9525 cm (55; inch) X 3.81 cm (lfz inches X0.317 cm (1% inch) S.A.E. 1020 mild steel coupon. A 0.317 cm diameterhold is drilled or punched through one end of the coupon not less than0.317 cm from the edge. Prior to use, this coupon is sandblasted andweighed. Contact with skin is avoided. The coupon remains in the systemovernight at which time it is removed from the flask, cleaned withcleansing powder to remove loose corrosion products, dipped withagitation in an inhibited acid bath for 30 seconds, in a saturated sodaash bath for seconds, washed in tap water to remove remaining salts,dipped with agitation in an acetone bath and spun dry. The coupon isthen dried in a 100C. oven for 30 minutes and reweighed. The corrosionrate is calculated on the basis of weight loss and test duration.

The corrosion rate ofthe product formed in Example 1 was 12 mpy at adosage of 12 ppm and 14 mpy at a dosage of 6 ppm.

' TABLE IV Surfactant No. Dosage (PPM) Corrosion Rate (MPY) 1 12 1 6 352 12 27 2 6 38 3 I2 29 3 6 37 4 12 23 4 6 39 It is observed from thedata presented in Table IV that in a refinery system the imidazolinesurfactant of this invention results in substantially improved corrosionrates.

I claim:

1. A process for the prevention of corrosion in refinery systemscomprising the step of injecting into the overhead vapor line of therefinery system a composition consisting of:

A. from 1040 percent by weight of an organic solvent; and

B. from 50-90 percent by weight of an imidazoline compound havingcorrosion inhibition properties, said compound formed by the reaction ofdipropylene triamine and a naphthenic acid in the ratios of \:2 to 2:1.

2. The process for the prevention of corrosion in refinery systems as inclaim 1 wherein the ratio of dipropylene triamine to naphthenic acid is1:2.

3. A process for the prevention of corrosion in refinery systems inrefinery processing comprising the step of injecting into the overheadvapor line of the refinery system a composition consisting of:

A. 20 percent by weight of an organic solvent; and

Bi percent by weight of an imidazoline surfactant having corrosioninhibition properties, said surfactant formed by the reaction ofdipropylene triamine and a naphthenic acid in the ratio of 1:2.

4. A process for the prevention of corrosion in refinery systems as inclaim 1 wherein from 2-5 ppm of the composition is injected into theoverhead vapor line.

2. The process for the prevention of corrosion in refinery systems as inclaim 1 wherein the ratio of dipropylene triamine to naphthenic acid is1:2.
 3. A process for the prevention of corrosion in refinery systems inrefinery processing comprising the step of injecting into the overheadvapor line of the refinery system a composition consisting of: A. 20percent by weight of an organic solvent; and B. 80 percent by weight ofan imidazoline surfactant having corrosion inhibition properties, saidsurfactant formed by the reaction of dipropylene triamine and anaphthenic acid in the ratio of 1:2.
 4. A process for the prevention ofcorrosion in refinery systems as in claim 1 wherein from 2-5 ppm of thecomposition is injected into the overhead vapor line.